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June 21, 2013

Xeon Phi : efficiency myth

Intel stated that it’s Xeon Phi would be more efficient than GPGPU for HPC. That Xeon Phi would have better linpack/watt and also beter linpack/raw TFlop ratio.

The first 2 supercomputers on the Top500 june’13 list are using Intel Xeon Phi and nVidia K20x respectively, so we could compare their metrics, and especially their efficiency.

The first point is Linpack TFlop/Watt, Xeon Phi delivers 33862 Linpack Tflops with 17808 KW (1.90 Tflop/KW), when K20x delivers 17590 Linpack Tflops with 8209 KW (2.14 Tflop/KW), the K20x architectured supercomputer is 12.7% more power efficient!

The second point is the ratio of RAW processing power compared to Linpack, to evaluate effectivness of an architecture, knowing that GPU aren’t as efficient as CPU, and that Intel claimed that with it’s x86 core, the Xeon Phi will be much more efficient than nVidia K20x, providing real-world performances closer than it’s peak theorical performance.

Alas on this second point, as I expected, Xeon Phi lag behind K20x another time, with 61.7% efficiency, where nVidia GPU obtains 64.9%, proving that the Intel architecture is not mature enough and still needs iterations.

Clearly, the K20x consume less power, and it’s architecture (hardware and software) is more mature and efficient than Intel Xeon Phi!

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